The "One Tree Hill" alum has given birth to a baby boy with husband Mike Caussin, she announced via Instagram on Thursday. Kramer Instagrammed a photo of the couple holding their son, whom they decided to name Jace, at the hospital.

"Welcome to the world Jace Joseph Caussin," she wrote. "Our hearts are so full. Thank you to all of our friends and family..and all of you who have supported Mike and I, and our growing family."

Kramer and Caussin, a former NFL player, are already parents to their 2-year-old daughter, Jolie. The two married in May 2015, but separated in August 2016 before reconciling.

"Surprise! We have a rainbow baby on the way & couldn’t be more excited!" she wrote on Instagram next to a family photo of her and Caussin with Jolie in the middle. "Jolie is going to be a big sister & we’re becoming a family of 4!"

A "rainbow baby" is a term used for a baby born after a miscarriage, stillborn or neonatal death, named so because rainbows are almost always preceded by rainy or stormy weather.

One month after her pregnancy announcement, the "I Got the Boy" singer opened up about her miscarriages during an emotional vlog, sharing that she and Caussin initially had trouble conceiving and turned to In vitro fertilization for help.

Though Kramer did get pregnant from IVF, she went on to have a "very, very early chemical loss."

Later, she had a miscarriage after she conceived naturally just months after Jolie was born, and then suffered another miscarriage last October.

"It's sad because when you find out you're pregnant it's so exciting and you want to shout it and tell everybody, but you don't because of stuff like this," Kramer said while shedding tears in the video.